The expression and roles of Id1 and Id2 in the aggressive phenotype of human oral squamous cell carcinoma cells

Abstract Objective Id (inhibitor of DNA binding or differentiation) proteins are dominant-negative regulators of basic helix-loop-helix transcription factors that control malignant cell behavior in many different tissues. The study aim was to investigate the effects of Id on human oral squamous cell carcinoma (OSCC) cells. Materials and methods The expression spectrum of Id1 and Id2 was examined in 6 different OSCC cell lines. Next, antisense vector infection or siRNA-mediated gene silencing was used to knockdown Id1 and Id2 expression in the SAS and HSC-2 cell lines (only Id1) to determine the effects on proliferation and invasion in vitro. Results The poorly differentiated SAS cell line and the differentiated HSC-2 cell line abundantly expressed Id1, whereas the other 4 cell lines showed little or undetectable Id1 expression. Id2 was generally expressed at a lower level than Id1 in the SAS cell line but showed little to no expression in the other OSCC cell lines. The knockdown of Id1 significantly repressed cell proliferation and invasion and decreased telomerase activities in the SAS and HSC-2 cell lines, whereas the knockdown of Id2 in the SAS cell lines showed no effect on proliferation and invasion. Conclusion We conclude that Id1 plays a more important role than Id2 in the proliferation and invasion of human OSCC cells.